The present invention generally relates to helical scan type magnetic recording and reproducing apparatuses, and more particularly to a helical scan type magnetic recording and reproducing apparatus which can satisfactorily reproduce a recorded signal from a magnetic tape for monitoring purposes while recording a signal on the magnetic tape and satisfactorily carry out an editing operation such as an insert recording while reproducing a recorded signal from the magnetic tape.
Conventionally, there is a helical scan type magnetic recording and reproducing apparatus for recording and reproducing video and/or audio signals on and from a magnetic tape by use of rotary heads which form tracks obliquely to a longitudinal direction of the magnetic tape. As will be described later on in the present specification in conjunction with a drawing, the conventional apparatus comprises a first pair of rotary heads mounted at mutually opposing positions on a rotary drum and a second pair of rotary heads mounted at mutually opposing positions on the rotary drum. The first pair of rotary heads respectively lead the second pair of rotary heads by an angle less than 90.degree. along a rotating direction of the rotary drum. The first and second pairs of rotary heads are all mounted at the same height position along an axial direction of the rotary drum. A magnetic tape is wrapped obliquely around a peripheral surface of the rotary drum for an angular range of approximately 180.degree. and is transported in a predetermined direction. When reproducing recorded signals for monitoring purposes while recording signals on the magnetic tape, the second pair of rotary heads scan over the tracks formed by the first pair of rotary heads so as to reproduce the recorded signals.
However, according to the conventional apparatus, it is difficult to carry out an editing operation such as an insert recording while reproducing recorded signals from the magnetic tape. Especially in the case of a pingpong operation in which a first rotary head reproduces a recorded signal from the magnetic tape and a second rotary head records on the magnetic tape a signal which is obtained by subjecting the reproduced signal from the first rotary head to a predetermined signal processing, a time interval between a time when the first rotary head finishes reproducing the recorded signal from a predetermined track on the magnetic tape and a time when the second rotary head starts to record on the predetermined track the signal which is obtained by subjecting the reproduced signal from the first rotary head to the predetermined signal processing is extremely short and is insufficient for carrying out the predetermined signal processing. In addition, when recording a digital signal which is reproduced from the magnetic tape, it is necessary to reserve a time it takes to decode and demodulate the reproduced digital signal and a time it takes to encode and modulate the digital signal which is to be recorded. For this reason, it is impossible to carry out an editing operation such as the pingpong operation in the conventional apparatus.